Systems and methods for source switching and voltage generation

ABSTRACT

System and method for regulating a power conversion system. An example system controller for regulating a power conversion system includes a first controller terminal associated with a first controller voltage and coupled to a first transistor terminal of a first transistor, the first transistor further including a second transistor terminal and a third transistor terminal, the second transistor terminal being coupled to a primary winding of a power conversion system, a second controller terminal associated with a second controller voltage and coupled to the third transistor terminal, and a third controller terminal associated with a third controller voltage. The first controller voltage is equal to a sum of the third controller voltage and a first voltage difference. The second controller voltage is equal to a sum of the third controller voltage and a second voltage difference.

1. CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims priority to Chinese Patent Application No.201210564309.4, filed Dec. 21, 2012, incorporated by reference hereinfor all purposes.

2. BACKGROUND OF THE INVENTION

The present invention is directed to integrated circuits. Moreparticularly, the invention provides systems and methods for sourceswitching and/or internal voltage generation. Merely by way of example,the invention has been applied to a power conversion system. But itwould be recognized that the invention has a much broader range ofapplicability.

Conventional switch-mode power supplies often implement gate controlledswitching using high voltage power MOSFETs. But high voltage start-upcircuits for such switch-mode power supplies are usually manufacturedusing an expensive high voltage semiconductor process. In addition, theconventional switch-mode power supplies often suffer from slow start-upand high standby power consumption.

Hence, it is highly desirable to improve switching schemes of a powerconversion system.

3. BRIEF SUMMARY OF THE INVENTION

The present invention is directed to integrated circuits. Moreparticularly, the invention provides systems and methods for sourceswitching and/or internal voltage generation. Merely by way of example,the invention has been applied to a power conversion system. But itwould be recognized that the invention has a much broader range ofapplicability.

According to one embodiment, a system controller for regulating a powerconversion system includes a first controller terminal associated with afirst controller voltage and coupled to a first transistor terminal of afirst transistor, the first transistor further including a secondtransistor terminal and a third transistor terminal, the secondtransistor terminal being coupled to a primary winding of a powerconversion system, a second controller terminal associated with a secondcontroller voltage and coupled to the third transistor terminal, and athird controller terminal associated with a third controller voltage.The first controller voltage is equal to a sum of the third controllervoltage and a first voltage difference. The second controller voltage isequal to a sum of the third controller voltage and a second voltagedifference. The system controller is configured to, keep the firstvoltage difference constant and change the second voltage difference toturn on or off the first transistor and to affect a primary currentflowing through the primary winding.

According to another embodiment, a system controller for regulating apower conversion system includes a first controller terminal associatedwith a first controller voltage and coupled to a first transistorterminal of a first transistor, the first transistor further including asecond transistor terminal and a third transistor terminal, the secondtransistor terminal being coupled to a primary winding of a powerconversion system, a second controller terminal associated with a secondcontroller voltage and coupled to the third transistor terminal and afirst capacitor terminal of a first capacitor, and a third controllerterminal associated with a third controller voltage. The systemcontroller further includes a second transistor including a fourthtransistor terminal, a fifth transistor terminal and a sixth transistorterminal, the fifth transistor terminal being coupled to the secondcontroller terminal, and a first clamping component including a firstcomponent terminal and a second component terminal, the first componentterminal being coupled to the first controller terminal.

According to yet another embodiment, a system controller for regulatinga power conversion system includes a first controller terminalassociated with a first controller voltage and coupled to a firsttransistor terminal of a first transistor, the first transistor furtherincluding a second transistor terminal and a third transistor terminal,the second transistor terminal being coupled to a primary winding of apower conversion system, a second controller terminal associated with asecond controller voltage and coupled to the third transistor terminal,the second controller terminal being further coupled to a firstcapacitor terminal of a first capacitor through a diode, and a thirdcontroller terminal associated with a third controller voltage. Thesystem controller further includes a second transistor including afourth transistor terminal, a fifth transistor terminal and a sixthtransistor terminal, the fifth transistor terminal being coupled to thesecond controller terminal, and the diode including an anode terminaland a cathode terminal, the cathode terminal being coupled to the firstcapacitor terminal, the anode terminal being coupled to the secondcontroller terminal. The system controller is configured to charge thefirst capacitor through the diode in response to one or more currentspikes.

According to yet another embodiment, a system controller for regulatinga power conversion system includes, a first controller terminalassociated with a first controller voltage and coupled to a firsttransistor terminal of a first transistor, the first transistor furtherincluding a second transistor terminal and a third transistor terminal,the second transistor terminal being coupled to a primary winding of thepower conversion system, a second controller terminal associated with asecond controller voltage and coupled to the third transistor terminal,and a third controller terminal associated with a third controllervoltage. The system controller further includes a fourth controllerterminal associated with a fourth controller voltage and coupled to afirst capacitor terminal of a capacitor, the capacitor further includinga second capacitor terminal coupled to the third controller terminal, asecond transistor including a fourth transistor terminal, a fifthtransistor terminal and a sixth transistor terminal, the fifthtransistor terminal being coupled to the second controller terminal, anda switch configured to received a control signal and including a firstswitch terminal and a second switch terminal, the first switch terminalcoupled to the second controller terminal, the second switch terminalcoupled to the fourth controller terminal. The system controller isconfigured to close the switch if the second transistor is turned on andif the fourth controller voltage is smaller than a first threshold.

In one embodiment, a system controller for regulating a power conversionsystem includes, a first controller terminal associated with a firstcontroller voltage and coupled to a first transistor terminal of a firsttransistor, the first transistor further including a second transistorterminal and a third transistor terminal, the third transistor terminalbeing coupled to a primary winding of the power conversion system, asecond transistor including a fourth transistor terminal, a fifthtransistor terminal and a sixth transistor terminal, the sixthtransistor terminal coupled to a first resistor, and a first clampingcomponent coupled to the fourth transistor terminal. The first clampingcomponent is configured to receive a current associated with the firstcontroller voltage, generate a reference voltage based on at leastinformation associated with the current, and bias the fourth transistorterminal to the reference voltage to generate a supple voltage at thefifth transistor terminal.

In another embodiment, a method for regulating a power conversion systemincluding a system controller with a first controller terminal, a secondcontroller terminal and a third controller terminal, includes,generating a first controller voltage associated with the firstcontroller terminal coupled to a first transistor terminal of a firsttransistor, the first transistor further including a second transistorterminal and a third transistor terminal, the second transistor terminalbeing coupled to a primary winding of the power conversion system,generating a second controller voltage associated with the secondcontroller terminal coupled to the third transistor terminal, andgenerating a third controller voltage associated with the thirdcontroller terminal. The method further includes processing informationassociated with the first controller voltage, the second controllervoltage and the third controller voltage, the first controller voltagebeing equal to a sum of the third controller voltage and a first voltagedifference, the second controller voltage is equal to a sum of the thirdcontroller voltage and a second voltage difference, keeping the firstvoltage difference constant, and changing the second voltage differenceto turn on or off the first transistor to affect a primary currentflowing through the primary winding.

In yet another embodiment, a method for regulating a power conversionsystem including a system controller with a controller terminalincludes, generating a controller voltage associated with the controllerterminal coupled to a first transistor terminal of a first transistor,the first transistor further including a second transistor terminal anda third transistor terminal, the third transistor terminal being coupledto a primary winding of the power conversion system, generating acurrent associated with the controller voltage, biasing a fourthtransistor terminal of a second transistor to a reference voltage basedon at least information associated with the current, the secondtransistor further including a fifth transistor terminal and a sixthtransistor terminal, the sixth transistor terminal being coupled to aresistor, and generating a supply voltage at the fifth transistorterminal based on at least information associated with the referencevoltage.

According to another embodiment, a system controller for regulating apower conversion system includes a controller terminal associated with acontroller voltage and coupled to a first transistor terminal of a firsttransistor, the first transistor further including a second transistorterminal and a third transistor terminal, the third transistor terminalbeing coupled to a primary winding of the power conversion system, afirst resistor coupled to the controller terminal, and a clampingcomponent coupled to the first resistor. The clamping component isconfigured to receive a current from the first resistor associated withthe controller voltage, generate a reference voltage based on at leastinformation associated with the current, and output the referencevoltage to a voltage regulator.

According to yet another embodiment, a method for regulating a powerconversion system including a system controller with a controllerterminal includes, generating a controller voltage associated with thecontroller terminal coupled to a first transistor terminal of a firsttransistor, the first transistor further including a second transistorterminal and a third transistor terminal, the third transistor terminalbeing coupled to a primary winding of the power conversion system,generating a current associated with the controller voltage, the currentflowing through a resistor coupled to the controller terminal,generating a reference voltage based on at least information associatedwith the current, and outputting the reference voltage to a voltageregulator.

Many benefits are achieved by way of the present invention overconventional techniques. For example, some embodiments of the presentinvention provide a scheme of source switching using an internaltransistor in a system controller. In another example, certainembodiments of the present invention provide systems and methods forreducing an under-voltage lockout (UVLO) threshold voltage, e.g., closeto an internal supply voltage. In yet another example, some embodimentsof the present invention provide systems and methods for charging acapacitor quickly during a start-up process to provide a supply voltageusing a conduction current of a transistor.

Depending upon embodiment, one or more of these benefits may beachieved. These benefits and various additional objects, features andadvantages of the present invention can be fully appreciated withreference to the detailed description and accompanying drawings thatfollow.

4. BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified diagram showing a power conversion system withsource switching and/or internal voltage generation according to anembodiment of the present invention.

FIG. 2 is a simplified diagram showing certain components of thecontroller 102 as part of the power conversion system 100 according toan embodiment of the present invention.

FIG. 3(a) is a simplified diagram showing certain components of thecontroller 102 as part of the power conversion system 100 according toanother embodiment of the present invention.

FIG. 3(b) is a simplified diagram showing certain components of thecontroller 102 as part of the power conversion system 100 according toyet another embodiment of the present invention.

FIG. 4 is a simplified diagram showing certain components of thecontroller 102 as part of the power conversion system 100 according toyet another embodiment of the present invention.

FIG. 5 is a simplified diagram showing certain components of thecontroller 102 as part of the power conversion system 100 according toyet another embodiment of the present invention.

5. DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed to integrated circuits. Moreparticularly, the invention provides systems and methods for sourceswitching and/or internal voltage generation. Merely by way of example,the invention has been applied to a power conversion system. But itwould be recognized that the invention has a much broader range ofapplicability.

FIG. 1 is a simplified diagram showing a power conversion system withsource switching and/or internal voltage generation according to anembodiment of the present invention. This diagram is merely an example,which should not unduly limit the scope of the claims. One of ordinaryskill in the art would recognize many variations, alternatives, andmodifications.

The power conversion system 100 includes a controller 102, a primarywinding 142, a secondary winding 144, an auxiliary winding 146, a switch122, capacitors 120, 128, 134, 150, 154 and 158, resistors 124, 130,132, 136 and 152, a full wave rectifying bridge including diodes 160,162, 164 and 166, and diodes 126, 148 and 156. The controller 102includes terminals 104, 106, 108, 110, 112, 114, 116 and 118. Forexample, the system 100 provides power to one or more light emittingdiodes. In another example, the switch 122 is a transistor. In yetanother example, the switch 122 is a field effect transistor (e.g., ametal-oxide-semiconductor field effect transistor), including a terminal174 (e.g., drain terminal), a terminal 176 (e.g., gate terminal) and aterminal 178 (e.g., source terminal).

According to one embodiment, the transistor 122 is turned on and offbased on a difference between a voltage signal 182 at the terminal 176(e.g., gate terminal) and a voltage signal 180 at the terminal 178(e.g., source terminal). In another example, the system 100 performssource switching of the transistor 122 through changing the voltagesignal 180 at the terminal 178 (e.g., source terminal). In yet anotherexample, the system 100 performs source switching of the transistor 122through keeping the voltage signal 182 at the terminal 176 constant andchanging the voltage signal 180 at the terminal 178 (e.g., sourceterminal). In yet another example, the terminal 174 (e.g., drainterminal) of the transistor 122 is connected, directly or indirectly, tothe primary winding 142, and the terminal 176 (e.g., gate terminal) ofthe transistor 122 is connected to the terminal 116 (e.g., terminalGATE). In yet another example, the terminal 178 (e.g., source terminal)of the transistor 122 is connected to the terminal 118 (e.g., terminalSW).

As shown in FIG. 1, the full wave rectifying bridge including the diodes160, 162, 164 and 166 processes an AC input signal from an AC supplycomponent 170, and generates a voltage signal 172 in some embodiments.For example, the voltage signal 182 increases in magnitude in responseto the voltage signal 172 through the resistor 124 and the capacitor120, and eventually reaches a predetermined magnitude. In anotherexample, the voltage signal 182 is fixed at the predetermined magnitude.In yet another example, if the difference between the voltage signal 182and the voltage signal 180 is larger than a threshold, the transistor122 is turned on. In yet another example, a current 184 flows throughthe transistor 122 into the terminal 118 (e.g., terminal SW), and flowsout of the terminal 112 (e.g., terminal VDD) to charge the capacitor 128in order to provide a supply voltage for the controller 102.

In another embodiment, the system 100 performs internal voltagegeneration for the controller 102. For example, when the controller 102begins to operate normally, the charged capacitor 120 provides aninternal current in order to generate an internal supply voltage for thecontroller 102. In another example, the generated internal supplyvoltage is about 5 V. In yet another example, a supply voltage signal198 at the terminal 112 (e.g., terminal VDD) can be as low as theinternal supply voltage.

FIG. 2 is a simplified diagram showing certain components of thecontroller 102 as part of the power conversion system 100 according toan embodiment of the present invention. This diagram is merely anexample, which should not unduly limit the scope of the claims. One ofordinary skill in the art would recognize many variations, alternatives,and modifications. The controller 102 includes a voltage clamper 188(e.g., a zener diode), a diode 186, a driver component 190, and a switch192. For example, the switch 192 is a transistor. In another example,the switch 192 is a field effect transistor (e.g., a MOSFET).

As shown in FIG. 2, the driver component 190 affects a voltage signal194 at a terminal 193 (e.g., gate terminal) of the transistor 192 toturn on or off the transistor 192 according to certain embodiments. Forexample, when the transistor 192 is turned off, the transistor 122 isoff. In another example, when the transistor 192 is turned on, a voltage196 at the terminal 110 is approximately equal to the voltage signal 180and the transistor 122 is on if the difference between the voltagesignal 182 and the voltage signal 180 is larger than a threshold. In yetanother example, during the start-up process, the capacitor 120 ischarged in response to the voltage signal 172 and the voltage signal 182increases in magnitude. Once the voltage signal 182 reaches apredetermined magnitude, the voltage clamper 188 clamps (e.g., fixes)the voltage signal 182 at the predetermined magnitude (e.g., a breakdownvoltage of the voltage clamper 188) in some embodiments. For example, itwas clamped by the voltage clamper 188 in some embodiments. For example,the properties of the voltage clamper 188 affect the predeterminedmagnitude (e.g., 18 V). In another example, a maximum value of thevoltage signal 180 is equal to a sum of the voltage signal 182 and avoltage drop on the diode 186 in magnitude. In yet another example,during normal operations, the capacitor 120 continues to receiveelectric charges (e.g., from spikes resulting from the switching of thetransistor 122 and the transistor 192) to keep the voltage signal 182constant or substantially constant.

FIG. 3(a) is a simplified diagram showing certain components of thecontroller 102 as part of the power conversion system 100 according toanother embodiment of the present invention. This diagram is merely anexample, which should not unduly limit the scope of the claims. One ofordinary skill in the art would recognize many variations, alternatives,and modifications. The controller 102 includes a voltage clamper 202(e.g., a zener diode), diodes 204 and 212, a driver component 206, aswitch 208, an under-voltage lockout and low drop-out (UVLO & LDO)component 210, a resistor 213 and a switch 214. For example, the switch208 is a transistor. In another example, the switch 208 is a fieldeffect transistor (e.g., a MOSFET).

As shown in FIG. 3(a), the driver component 206 affects a voltage signal216 at a terminal 218 (e.g., gate terminal) of the transistor 208 toturn on or off the transistor 208 according to certain embodiments. Forexample, the status of the transistor 122 (e.g., on or off) depends onwhether the transistor 208 is turned on or off. In another example,during the start-up process, the voltage signal 182 increases inmagnitude in response to the voltage signal 172 through the resistor 124and the capacitor 120. Once the voltage signal 182 reaches apredetermined magnitude, the voltage clamper 202 (e.g., a zener diode)clamps (e.g., fixes) the voltage signal 182 at the predeterminedmagnitude (e.g., a breakdown voltage of the voltage clamper 202) in someembodiments. For example, the properties of the voltage clamper 202affect the predetermined magnitude (e.g., 18 V).

In one embodiment, when the difference between the voltage signal 182and the voltage signal 180 is larger than a threshold, the transistor122 begins to conduct a current 174 which flows through the terminal 118(e.g., terminal SW). In another example, if the switch 214 is closed(e.g., on) in response to a signal 222 (e.g., porB) generated by theUVLO & LDO component 210, the current 172 flows through the diode 212and the switch 214 to charge the capacitor 128 and a voltage signal 224at the terminal 112 (e.g., terminal VDD) increases in magnitude. In yetanother example, when the voltage signal 224 exceeds a firstpredetermined threshold voltage (e.g., an upper threshold) in magnitude,the UVLO & LDO component 210 changes the signal 222 to open (e.g., toturn off) the switch 214. In yet another example, if the voltage signal224 drops below a second predetermined threshold voltage (e.g., a lowerthreshold) in magnitude, the UVLO & LDO component 210 changes the signal222 to close (e.g., to turn on) the switch 214 in order to charge thecapacitor 128 again. In yet another example, the current 172 is limitedby at least the resistor 213 coupled between the terminal 118 (e.g.,terminal SW) and the terminal 112 (e.g., terminal VDD). In anotherexample, a maximum value of the voltage signal 180 is equal to a sum ofthe voltage signal 182 and a voltage drop on the diode 204 in magnitude.In yet another example, the first predetermined threshold voltage isdifferent from or the same as the second predetermined thresholdvoltage. The resistor 213 is omitted in some embodiments.

In another embodiment, the auxiliary winding 146 is removed, and theswitch 214 is always kept on. In yet another embodiment, the auxiliarywinding 146 and the switch 214 are removed, and the diode 212 is coupledbetween the terminal 118 and the terminal 112. For example, without theauxiliary winding 146, the supply voltage of the controller 102 isprovided through the transistor 122. In another example, the switch 214is implemented using a p-channel field effect transistor (e.g., ap-channel metal-oxide-semiconductor field effect transistor).

FIG. 3(b) is a simplified diagram showing certain components of thecontroller 102 as part of the power conversion system 100 according toyet another embodiment of the present invention. This diagram is merelyan example, which should not unduly limit the scope of the claims. Oneof ordinary skill in the art would recognize many variations,alternatives, and modifications. The controller 102 includes a voltageclamper 202 (e.g., a zener diode), diodes 204 and 212, a drivercomponent 206, a transistor 208, an under-voltage lockout and lowdrop-out (UVLO & LDO) component 210, a resistor 213, and a switch 214.In addition, the controller 102 includes a current source 230 and adiode 232. For example, the transistor 208 is a field effect transistor(e.g., a MOSFET).

According to one embodiment, the voltage signal 182 at the terminal 176(e.g., the gate terminal of the transistor 122) is kept no less than apredetermined level. For example, the diode 232 has a forward voltage(e.g., V_(f)). In another example, during normal operation of the powerconversion system 100, the voltage signal 224 at the terminal 112 (e.g.,terminal VDD) is no less than an under-voltage lockout voltage (e.g.,V_(UVLO)). Thus, a minimum of the voltage signal 182 is determined asfollows according to certain embodiments:

V _(GATE) ≧V _(UVLO) −V _(f)  (1)

where V_(GATE) represents the voltage signal 182. For example, when thevoltage signal 182 is lower in magnitude than the voltage signal 224minus the forward voltage of the diode 232, the capacitor 120 is chargedin response to a current 234 flowing from the terminal 112 (e.g.,terminal VDD) to the terminal 116 (e.g., terminal GATE) through thediode 232.

FIG. 4 is a simplified diagram showing certain components of thecontroller 102 as part of the power conversion system 100 according toyet another embodiment of the present invention. This diagram is merelyan example, which should not unduly limit the scope of the claims. Oneof ordinary skill in the art would recognize many variations,alternatives, and modifications. The controller 102 includes voltageclampers 302 and 332, diodes 304 and 312, a driver component 306,switches 308 and 334, an under-voltage lockout (UVLO) component 310, aswitch 314, and resistors 330 and 336. For example, the switches 308 and334 are transistors. In another example, the switch 308 is a fieldeffect transistor (e.g., a MOSFET). In another example, the switch 334is a field effect transistor (e.g., a MOSFET).

As shown in FIG. 4, the driver component 306 affects a voltage signal316 at a terminal 318 (e.g., gate terminal) of the transistor 308 toturn on or off the transistor 308 according to certain embodiments. Forexample, the status of the transistor 122 (e.g., on or off) depends onwhether the transistor 308 is turned on or off. In another example,during the start-up process, the voltage signal 182 increases inmagnitude in response to the voltage signal 172 through the resistor 124and the capacitor 120. Once the voltage signal 182 reaches apredetermined magnitude, the voltage clamper 302 clamps (e.g., fixes)the voltage signal 182 at the predetermined magnitude (e.g., a breakdownvoltage of the voltage clamper 302) in some embodiments.

In one embodiment, when the difference between the voltage signal 182and the voltage signal 180 is larger than a threshold, the transistor122 begins to conduct a current 174 which flows through the terminal 118(e.g., terminal SW). In another example, if the switch 314 is closed(e.g., on) in response to a signal 322 (e.g., porB) generated by theUVLO component 310, the current 172 flows through the diode 312 and theswitch 314 to charge the capacitor 128 and a voltage signal 324 at theterminal 112 (e.g., terminal VDD) increases in magnitude. In yet anotherexample, when the voltage signal 324 exceeds a first predeterminedthreshold voltage (e.g., an upper threshold) in magnitude, the UVLOcomponent 310 changes the signal 322 to open (e.g., to turn off) theswitch 314. In yet another example, if the voltage signal 324 dropsbelow a second predetermined threshold voltage (e.g., a lower threshold)in magnitude, the UVLO component 310 changes the signal 322 to close(e.g., to turn on) the switch 314 in order to charge the capacitor 128again. In yet another example, the first predetermined threshold voltageis different from or the same as the second predetermined thresholdvoltage.

In another embodiment, when the controller 102 begins to operatenormally, and the charged capacitor 120 provides a current 350 whichflows through the resistor 330. For example, a reference voltage signal352 (e.g., V_(ref)) is generated in response to the current 350 flowingfrom the resistor 330 to the voltage clamper 332. In some embodiments,the reference voltage signal 352 is provided to a voltage regulator as areference level. For example, the voltage regulator includes thetransistor 334 which is configured as a source follower. In anotherexample, the reference voltage signal 352 (e.g., V_(ref)) is generatedat a terminal 354 (e.g., gate terminal) of the transistor 334. In yetanother example, once the voltage signal 352 (e.g., V_(ref)) reaches apredetermined magnitude, the voltage clamper 332 clamps (e.g., fixes)the voltage signal 352 at the predetermined magnitude (e.g., a breakdownvoltage of the voltage clamper 332). In yet another example, if thetransistor 334 is turned on, a voltage signal 356 (e.g., AVDD) isgenerated at a terminal 358 of the transistor 334 through the resistor336. In yet another example, the voltage signal 356 (e.g., AVDD) is usedfor providing an internal supply voltage for the controller 102. In yetanother example, the signal 356 (e.g., AVDD) is an internal signal ofthe controller 102, e.g., an internal supply voltage.

V _(AVDD) =V _(ref) −V _(th)  (2)

where V_(ref) represents the reference voltage signal 352, and V_(th)represents a threshold voltage of the transistor 334.

For example, the breakdown voltage of the voltage clamper 332 (e.g., azener diode) is about 6 V, and a threshold voltage of the transistor 33d is about 1 V. The voltage signal 356 is generated to be about 5 V insome embodiments. For example, even if the voltage signal 324 is as lowas about 5 V, the transistor 334 can still generate the voltage signal356 at about 5 V by operating in a linear region. Thus, the secondpredetermined threshold voltage (e.g., the lower threshold) of the UVLOcomponent 310 can be reduced to a low magnitude (e.g., 5 V) in certainembodiments.

In yet another embodiment, during normal operations, the capacitor 120is charged in response to spikes generated at each switching of thetransistor 308 (e.g., M2) through the diode 304 (e.g., D2) in order tokeep the voltage signal 182 constant or substantially constant. Forexample, the resistor 124 has a large resistance in order to reducepower loss. In another example, the spikes are generated mainly when thetransistor 308 is turned off.

FIG. 5 is a simplified diagram showing certain components of thecontroller 102 as part of the power conversion system 100 according toyet another embodiment of the present invention. This diagram is merelyan example, which should not unduly limit the scope of the claims. Oneof ordinary skill in the art would recognize many variations,alternatives, and modifications. The controller 402 includes zenerdiodes 402, 432 and 462, diodes 404 and 412, a driver component 406,transistors 408 and 434, an under-voltage lockout (UVLO) component 410,switches 414, 464, 466 and 468, and resistors 430 and 436. For example,the transistor 408 is a field effect transistor (e.g., a MOSFET). Inanother example, the transistor 434 is a field effect transistor (e.g.,a MOSFET).

As shown in FIG. 5, the driver component 406 affects a voltage signal416 at a terminal 418 (e.g., gate terminal) of the transistor 408 toturn on or off the transistor 408 according to certain embodiments. Forexample, the status of the transistor 122 (e.g., on or off) depends onwhether the transistor 408 is turned on or off. In another example,during the start-up process, the voltage signal 182 increases inmagnitude in response to the voltage signal 172 through the resistor 124and the capacitor 120. Once the voltage signal 182 reaches apredetermined magnitude, it was clamped (e.g., fixed) by at least thezener diode 402 in some embodiments. For example, during the start-upprocess, a voltage signal 424 at the terminal 112 (e.g., terminal VDD)is lower than a first predetermined threshold voltage (e.g., an upperthreshold) in magnitude, and the UVLO component 410 generates a signal422 (e.g., porB) to close (e.g., to turn on) the switches 414 and 464and a signal 470 (e.g., por) to open (e.g., to turn off) the switches466 and 468. In another example, when the signal 422 is at a logic highlevel, the signal 470 is at a logic low level, and when the signal 422is at the logic low level, the signal 470 is at the logic high level.

In one embodiment, when the difference between the voltage signal 182and the voltage signal 180 is larger than a threshold, the transistor122 begins to conduct a current 174 which flows through the terminal 118(e.g., terminal SW). In another example, if the switch 414 is closed(e.g., on) in response to the signal 422 (e.g., porB), the current 172flows through the diode 412 and the switch 414 to charge the capacitor128 and the voltage signal 424 at the terminal 112 (e.g., terminal VDD)increases in magnitude. In yet another example, when the voltage signal424 exceeds the first predetermined threshold voltage in magnitude, theUVLO component 410 changes the signal 422 to open (e.g., to turn off)the switch 414. In yet another example, if the voltage signal 424 dropsbelow a second predetermined threshold voltage (e.g., a lower threshold)in magnitude, the UVLO component 410 changes the signal 422 to close(e.g., to turn on) the switch 414 in order to charge the capacitor 128again. In yet another example, if the voltage signal 424 exceeds thefirst predetermined threshold voltage in magnitude, the switch 466 isclosed (e.g., on) in response to the signal 470 generated by the UVLOcomponent 410, and the voltage signal 182 is clamped (e.g., fixed) bythe zener diode 402. In yet another example, if the voltage signal 424drops below the second predetermined threshold voltage in magnitude, theswitch 466 is opened (e.g., off) in response to the signal 470 generatedby the UVLO component 410, and the voltage signal 182 is clamped (e.g.,fixed) by both the zener diode 402 and the zener diode 462. In yetanother example, the first predetermined threshold voltage is differentfrom or the same as the second predetermined threshold voltage.

In another embodiment, when the controller 102 operates normally, if thevoltage signal 424 is larger than the first predetermined thresholdvoltage in magnitude, the switch 468 is closed (e.g., on) in response tothe signal 470 generated by the UVLO component 410 and the switch 464 isopened (e.g., off) in response to the signal 422. In another example,the charged capacitor 120 provides a current 450 which flows through theresistor 430. In yet another example, a reference voltage signal 452(e.g., V_(ref)) is generated in response to the current 450 flowing fromthe resistor 430 to the voltage clamper 432. In some embodiments, thereference voltage signal 452 is provided to a voltage regulator as areference level. For example, the voltage regulator includes thetransistor 434 which is configured as a source follower. In anotherexample, the reference voltage signal 452 is generated at a terminal 454(e.g., gate terminal) of the transistor 434. In yet another example, ifthe transistor 434 is turned on, a voltage signal 456 (e.g., AVDD) isgenerated at a terminal 458 of the transistor 434 through the resistor436. In yet another example, the signal 456 (e.g., AVDD) is an internalsignal of the controller 102, e.g., an internal supply voltage.

V _(AVDD) =V _(ref) −V _(th)  (3)

where V_(ref) represents the reference voltage signal 452, and V_(th)represents a threshold voltage of the transistor 434.

According to another embodiment, a system controller for regulating apower conversion system includes a first controller terminal associatedwith a first controller voltage and coupled to a first transistorterminal of a first transistor, the first transistor further including asecond transistor terminal and a third transistor terminal, the secondtransistor terminal being coupled to a primary winding of a powerconversion system, a second controller terminal associated with a secondcontroller voltage and coupled to the third transistor terminal, and athird controller terminal associated with a third controller voltage.The first controller voltage is equal to a sum of the third controllervoltage and a first voltage difference. The second controller voltage isequal to a sum of the third controller voltage and a second voltagedifference. The system controller is configured to, keep the firstvoltage difference constant and change the second voltage difference toturn on or off the first transistor and to affect a primary currentflowing through the primary winding. For example, the system controlleris implemented according to FIG. 1, FIG. 2, FIG. 3(a), FIG. 3(b), FIG.4, and/or FIG. 5.

According to yet another embodiment, a system controller for regulatinga power conversion system includes a first controller terminalassociated with a first controller voltage and coupled to a firsttransistor terminal of a first transistor, the first transistor furtherincluding a second transistor terminal and a third transistor terminal,the second transistor terminal being coupled to a primary winding of apower conversion system, a second controller terminal associated with asecond controller voltage and coupled to the third transistor terminaland a first capacitor terminal of a first capacitor, and a thirdcontroller terminal associated with a third controller voltage. Thesystem controller further includes a second transistor including afourth transistor terminal, a fifth transistor terminal and a sixthtransistor terminal, the fifth transistor terminal being coupled to thesecond controller terminal, and a first clamping component including afirst component terminal and a second component terminal, the firstcomponent terminal being coupled to the first controller terminal. Forexample, the system controller is implemented according to at least FIG.2, FIG. 3(a), FIG. 3(b), FIG. 4, and/or FIG. 5.

According to yet another embodiment, a system controller for regulatinga power conversion system includes a first controller terminalassociated with a first controller voltage and coupled to a firsttransistor terminal of a first transistor, the first transistor furtherincluding a second transistor terminal and a third transistor terminal,the second transistor terminal being coupled to a primary winding of apower conversion system, a second controller terminal associated with asecond controller voltage and coupled to the third transistor terminal,the second controller terminal being further coupled to a firstcapacitor terminal of a first capacitor through a diode, and a thirdcontroller terminal associated with a third controller voltage. Thesystem controller further includes a second transistor including afourth transistor terminal, a fifth transistor terminal and a sixthtransistor terminal, the fifth transistor terminal being coupled to thesecond controller terminal, and the diode including an anode terminaland a cathode terminal, the cathode terminal being coupled to the firstcapacitor terminal, the anode terminal being coupled to the secondcontroller terminal. The system controller is configured to charge thefirst capacitor through the diode in response to one or more currentspikes. For example, the system controller is implemented according toat least FIG. 2, FIG. 3(a), FIG. 3(b), FIG. 4, and/or FIG. 5.

According to yet another embodiment, a system controller for regulatinga power conversion system includes, a first controller terminalassociated with a first controller voltage and coupled to a firsttransistor terminal of a first transistor, the first transistor furtherincluding a second transistor terminal and a third transistor terminal,the second transistor terminal being coupled to a primary winding of thepower conversion system, a second controller terminal associated with asecond controller voltage and coupled to the third transistor terminal,and a third controller terminal associated with a third controllervoltage. The system controller further includes a fourth controllerterminal associated with a fourth controller voltage and coupled to afirst capacitor terminal of a capacitor, the capacitor further includinga second capacitor terminal coupled to the third controller terminal, asecond transistor including a fourth transistor terminal, a fifthtransistor terminal and a sixth transistor terminal, the fifthtransistor terminal being coupled to the second controller terminal, anda switch configured to received a control signal and including a firstswitch terminal and a second switch terminal, the first switch terminalcoupled to the second controller terminal, the second switch terminalcoupled to the fourth controller terminal. The system controller isconfigured to close the switch if the second transistor is turned on andif the fourth controller voltage is smaller than a first threshold. Forexample, the system controller is implemented according to at least FIG.3(a), FIG. 3(b), FIG. 4, and/or FIG. 5.

In one embodiment, a system controller for regulating a power conversionsystem includes, a first controller terminal associated with a firstcontroller voltage and coupled to a first transistor terminal of a firsttransistor, the first transistor further including a second transistorterminal and a third transistor terminal, the third transistor terminalbeing coupled to a primary winding of the power conversion system, asecond transistor including a fourth transistor terminal, a fifthtransistor terminal and a sixth transistor terminal, the sixthtransistor terminal coupled to a first resistor, and a first clampingcomponent coupled to the fourth transistor terminal. The first clampingcomponent is configured to receive a current associated with the firstcontroller voltage, generate a reference voltage based on at leastinformation associated with the current, and bias the fourth transistorterminal to the reference voltage to generate a supple voltage at thefifth transistor terminal. For example, the system controller isimplemented according to at least FIG. 4, and/or FIG. 5.

In another embodiment, a method for regulating a power conversion systemincluding a system controller with a first controller terminal, a secondcontroller terminal and a third controller terminal, includes,generating a first controller voltage associated with the firstcontroller terminal coupled to a first transistor terminal of a firsttransistor, the first transistor further including a second transistorterminal and a third transistor terminal, the second transistor terminalbeing coupled to a primary winding of the power conversion system,generating a second controller voltage associated with the secondcontroller terminal coupled to the third transistor terminal, andgenerating a third controller voltage associated with the thirdcontroller terminal. The method further includes processing informationassociated with the first controller voltage, the second controllervoltage and the third controller voltage, the first controller voltagebeing equal to a sum of the third controller voltage and a first voltagedifference, the second controller voltage is equal to a sum of the thirdcontroller voltage and a second voltage difference, keeping the firstvoltage difference constant, and changing the second voltage differenceto turn on or off the first transistor to affect a primary currentflowing through the primary winding. For example, the method isimplemented according to FIG. 1, FIG. 2, FIG. 3(a), FIG. 3(b), FIG. 4,and/or FIG. 5.

In yet another embodiment, a method for regulating a power conversionsystem including a system controller with a controller terminalincludes, generating a controller voltage associated with the controllerterminal coupled to a first transistor terminal of a first transistor,the first transistor further including a second transistor terminal anda third transistor terminal, the third transistor terminal being coupledto a primary winding of the power conversion system, generating acurrent associated with the controller voltage, biasing a fourthtransistor terminal of a second transistor to a reference voltage basedon at least information associated with the current, the secondtransistor further including a fifth transistor terminal and a sixthtransistor terminal, the sixth transistor terminal being coupled to aresistor, and generating a supply voltage at the fifth transistorterminal based on at least information associated with the referencevoltage. For example, the method is implemented according to at leastFIG. 4, and/or FIG. 5.

According to another embodiment, a system controller for regulating apower conversion system includes a controller terminal associated with acontroller voltage and coupled to a first transistor terminal of a firsttransistor, the first transistor further including a second transistorterminal and a third transistor terminal, the third transistor terminalbeing coupled to a primary winding of the power conversion system, afirst resistor coupled to the controller terminal, and a clampingcomponent coupled to the first resistor. The clamping component isconfigured to receive a current from the first resistor associated withthe controller voltage, generate a reference voltage based on at leastinformation associated with the current, and output the referencevoltage to a voltage regulator. For example, the system controller isimplemented according to at least FIG. 4, and/or FIG. 5.

According to yet another embodiment, a method for regulating a powerconversion system including a system controller with a controllerterminal includes, generating a controller voltage associated with thecontroller terminal coupled to a first transistor terminal of a firsttransistor, the first transistor further including a second transistorterminal and a third transistor terminal, the third transistor terminalbeing coupled to a primary winding of the power conversion system,generating a current associated with the controller voltage, the currentflowing through a resistor coupled to the controller terminal,generating a reference voltage based on at least information associatedwith the current, and outputting the reference voltage to a voltageregulator. For example, the method is implemented according to at leastFIG. 4, and/or FIG. 5.

For example, some or all components of various embodiments of thepresent invention each are, individually and/or in combination with atleast another component, implemented using one or more softwarecomponents, one or more hardware components, and/or one or morecombinations of software and hardware components. In another example,some or all components of various embodiments of the present inventioneach are, individually and/or in combination with at least anothercomponent, implemented in one or more circuits, such as one or moreanalog circuits and/or one or more digital circuits. In yet anotherexample, various embodiments and/or examples of the present inventioncan be combined.

Although specific embodiments of the present invention have beendescribed, it will be understood by those of skill in the art that thereare other embodiments that are equivalent to the described embodiments.Accordingly, it is to be understood that the invention is not to belimited by the specific illustrated embodiments, but only by the scopeof the appended claims.

1. A system controller for regulating a power conversion system, thesystem controller comprising: a first controller terminal associatedwith a first controller voltage and coupled to a first transistorterminal of a first transistor, the first transistor further including asecond transistor terminal and a third transistor terminal, the secondtransistor terminal being coupled to a primary winding of a powerconversion system; a second controller terminal associated with a secondcontroller voltage and coupled to the third transistor terminal; and athird controller terminal associated with a third controller voltage;wherein: the first controller voltage is equal to a sum of the thirdcontroller voltage and a first voltage difference; and the secondcontroller voltage is equal to a sum of the third controller voltage anda second voltage difference; wherein the system controller is configuredto: keep the first voltage difference constant; and change the secondvoltage difference to turn on or off the first transistor and to affecta primary current flowing through the primary winding.
 2. The systemcontroller of claim 1 wherein the first controller terminal is coupledto a first capacitor terminal of a capacitor, the capacitor furtherincluding a second capacitor terminal coupled to the third controllerterminal.
 3. The system controller of claim 1, and further comprising aswitch including a first switch terminal and a second switch terminal,the first switch terminal being coupled to the second controllerterminal; wherein the switch is configured to change the second voltagedifference to turn on or off the first transistor and to affect aprimary current flowing through the primary winding.
 4. The systemcontroller of claim 3 wherein the second switch terminal is coupled to afourth controller terminal configured to detect a sensing signalassociated with the primary current flowing through the primary winding.5. The system controller of claim 3 wherein the switch includes a secondtransistor.
 6. The system controller of claim 1 is further configured tokeep the first voltage difference from exceeding a predeterminedthreshold.
 7. A system controller for regulating a power conversionsystem, the system controller comprising: a first controller terminalassociated with a first controller voltage and coupled to a firsttransistor terminal of a first transistor, the first transistor furtherincluding a second transistor terminal and a third transistor terminal,the second transistor terminal being coupled to a primary winding of apower conversion system; a second controller terminal associated with asecond controller voltage and coupled to the third transistor terminaland a first capacitor terminal of a first capacitor; a third controllerterminal associated with a third controller voltage; a second transistorincluding a fourth transistor terminal, a fifth transistor terminal anda sixth transistor terminal, the fifth transistor terminal being coupledto the second controller terminal; and a first clamping componentincluding a first component terminal and a second component terminal,the first component terminal being coupled to the first controllerterminal.
 8. The system controller of claim 7 wherein: the secondcontroller voltage is equal to a sum of the third controller voltage anda second voltage difference; and the second transistor is configured tochange the second voltage difference to turn on or off the firsttransistor and to affect a primary current flowing through the primarywinding.
 9. The system controller of claim 8 wherein: the firstcontroller voltage is equal to a sum of the third controller voltage anda first voltage difference; and the first clamping component isconfigured to keep the first voltage difference from exceeding apredetermined threshold.
 10. The system controller of claim 7 whereinthe second component terminal is coupled to the third controllerterminal.
 11. The system controller of claim 7, and further comprising:a second clamping component including a third component terminal and afourth component terminal; a switch configured to received a controlsignal and including a first switch terminal and a second switchterminal, the first switch terminal coupled to the second componentterminal and the third component terminal, the second switch terminalcoupled to the fourth component terminal; and a fourth controllerterminal associated with a fourth controller voltage and coupled to athird capacitor terminal of a second capacitor, the second capacitorfurther including a fourth capacitor terminal coupled to the thirdcontroller terminal; wherein the system controller is configured to: ifthe fourth controller voltage is larger than a threshold, close theswitch to short the second clamping component; and if the fourthcontroller voltage is lower than a threshold, open the switch to connectthe second clamping component with the first clamping component.
 12. Thesystem controller of claim 7 wherein the second controller terminal iscoupled to the first capacitor terminal through a diode, the diodeincluding an anode terminal and a cathode terminal, the cathode terminalbeing coupled to the first capacitor terminal, the anode terminal beingcoupled to the second controller terminal.
 13. The system controller ofclaim 7, and further comprising a resistor including a first resistorterminal and a second resistor terminal, the first resistor terminalbeing coupled to the primary winding, the second resistor terminal beingcoupled to the first capacitor terminal.
 14. A system controller forregulating a power conversion system, the system controller comprising:a first controller terminal associated with a first controller voltageand coupled to a first transistor terminal of a first transistor, thefirst transistor further including a second transistor terminal and athird transistor terminal, the second transistor terminal being coupledto a primary winding of a power conversion system; a second controllerterminal associated with a second controller voltage and coupled to thethird transistor terminal, the second controller terminal being furthercoupled to a first capacitor terminal of a first capacitor through adiode; a third controller terminal associated with a third controllervoltage; a second transistor including a fourth transistor terminal, afifth transistor terminal and a sixth transistor terminal, the fifthtransistor terminal being coupled to the second controller terminal; andthe diode including an anode terminal and a cathode terminal, thecathode terminal being coupled to the first capacitor terminal, theanode terminal being coupled to the second controller terminal; whereinthe system controller is configured to charge the first capacitorthrough the diode in response to one or more current spikes.
 15. Thesystem controller of claim 14 wherein the one or more current spikes aregenerated if the first transistor changes from being turned on to beingturned off.
 16. The system controller of claim 14 wherein the one ormore current spikes are generated when the second transistor changesfrom being turned on to being turned off.
 17. The system controller ofclaim 14, and further comprising a first clamping component including afirst component terminal and a second component terminal, the firstcomponent terminal being coupled to the first controller terminal;wherein: the second controller voltage is equal to a sum of the thirdcontroller voltage and a second voltage difference; and the secondtransistor is configured to change the second voltage difference to turnon or off the first transistor and to affect a primary current flowingthrough the primary winding.
 18. The system controller of claim 17wherein: the first controller voltage is equal to a sum of the thirdcontroller voltage and a first voltage difference; and the firstclamping component is configured to keep the first voltage differencefrom exceeding a predetermined threshold. 19.-37. (canceled)